Wood grinder



1,614 162 Jan. 11 1927. W. STIEL WOOD GRINDER Filed March 51, 1926 L g 0 a 23 WITNESSE: INVENTOR I Wilhelm Shel.

BY Z ATT'ORNEY Patented Jan. 11, 1927.

UNITED STATES 1,614,162 PATENT OFFICE.

WILHELM STIEL, F BERLIN-SIEMENSSTADT, GERMANY, ASSIGNOR TO WESTING- HOUSE ELECTRIC & MANUFACTURING COMPANY, OF NEW YORK, N. Y., A CORPORA- WOOD GRINDER.

Application filed March 31. 1926, Serial No. 95,664, and inGermany March 31. 1325.

My invention relates to wood-gn'inders with a plurality of grindstones or abrading wheels driven from a common supply of energy. In such grinders as in grinders with a single grindstone or abrading wheel only, the load on the grinding motor is pretcrably kept approximately constant by correspondingly regulating the pressure with which the wood is forced against the indi; vidual grindstones or wheels. For keeping the output of the main driving motor constant, it is in itself sufficient to regulate the total of the pressures at the individual grindstones for constant load, It may, however, happen that the distribution of the load at the individual grindstones on wheels is very different. for instance. it at one grindstone a particularly high friction resistance develops owing to the stone encountering a branch in the wood, while another grindstone encounters cavities contained within the wood fed forward, so that i the grindstone is only in contact with por- 'tions of the wood and the resistance is very r small. The ground wood or pulp will then show an undesirable degree of irregularity.

It has therefore already been proposed to employ for the application pressure at the individual grindstones electric motors of such a characteristic, that their output remains constant irrespective of the application pressure for the time being or the change of speed. Not taking into consideration that such motors are expensive and that for connecting them with the supply of the main 'motor upon which they must depend, additional apparatus, such as transformers and the like are necessary, the output can really ogly be kept constant within a relatively narrow range;

In contrast with the known arrangement, I solve the problem by my invention in providing for each feed motor a regulating device which is controlled on the one hand by the load on the main drive and on the other hand by the load of the other food motors. In this manner it is possible to use as feed motors ordinary regulable motors, the regulation of which requires small currents, so that the plant is ,not rendered substantially more expensive by'the provision of the regulation apparatus. The control of the regulating apparatus may be efiected by the stator as well as by the rotor current of the feed motors. When ulation the advantage is attained in comparison with the stator current, that thewattless currents play no part, This arrangement appears therefore according to my invention particularly useful.

In the single figure of the drawing an embodiment of my invention is illustrated diagrammatically by way of example in simplified representation.

The main driving or primary motor 1, which in the illustrated embodiment is contemplated for the drive of two grindstoncs, is fed from the supply system 2. The feed of the wood in the grinder magazines is effected by the secondary or feed motors 3 and 4, the regulators 5 and 6 of which are operated in known manner by auxiliary motors .7 and 8. These auxiliary motors 7 and 8 are controlled by relays 9 and 10. The relays are controlled on the one hand from the load of the main driving motor and onthe other hand from the load of the feed motor appertaining to the other relay. The dependance from the grinding motor may, for instance, be brought about by a tap from a shunt 11 or a transformer in the supply lead of the primary motor. For this purpose the relays 9 and are equipped with coils 19 and 20 which by means of a regulator 12 or the like can be adapted to relatively predetermined load conditions. Each of the relays 9 and 10 is furthermore provided with an additional coil 29 and 30 which in the embodiment illustrated are controlled by the rotor current of theother feed'motor 4 or 3. The relays thus represent differential arrangements. When equilibrium prevails, i. e., when the loads are properly distributed, the contact tongue of the relay is located between the regulator contacts 13 and 23 of the auxiliary motors 7 and 8, When the load of one of the feed motors changes, its rotor current also changes and the relay appertaining to the other feed motor'responds and controls its feed motor in such a manner that its load is adapted to that of the former motor. The coils 19 and 20 of the relay then take care that the load of the main driving motor is kept constant by the feed motors.

The embodiment illustrated in the drawing is, of course, only an example of carry ing out the invention and the invention may be realized by means of other regulator systhe principle of my control system.

toms of known kind without departing from The system may naturally equally well be applied to. a difi'erent number of grindstones, provided care is taken that each feed 'motor is able to control the regulating devices of the other motors either directly or indirectly.

The control system according to my invention permits extraordinary. extensive fluctuations in the individual magazines and thus ensures the constancy of the load of the main motor Within Widest limits.

Various modifications and changes may be made Without departing from the spirit and scope bf the invention, and I desire, therefore, that only such limitations shall be placed thereon as are imposed by the prior art.

Iclaim as my invention 1. In an electric feed control system for Wood-grinders, a plurality of grindstones adapted to be operated from a common supply of electricity, electric motors for feeding the wood in dependance from the load of the electric main driving motor and a regulating device'for each of said feed motors, said devices being adapted to be controlled on the one hand by a load of the main driving motor and on the other hand by the load of the remaining feed motors.

2. In an electric feed control system for wood-grinders, a plurality of grindstones adapted" to be operated from a common sup ly of electricity, electric motors for fee ing the wood in dependance from the load of the electric main driving motor, a

regulating device for each of said feed motors, said devices being adapted to be controlled on the one hand by the load of the main driving motor and on the other hand by the load of the remaining feed motors, the rotor current of said motors being employed for the control of said regulating devices.

3. In an electric feed .control system for wood-grinders, a main driving motor adapted to be connected with a supply and to drive a plurality of grindstones, motors for feeding the wood forward in the grinder magazines, regulators for said motors, auxiliary motors for operating said regulators and relays for controlling said auxiliary motors, said relays being dependent on the one hand from the load of said main motor and on the other hand from the load of the remaining feed motors.

4. In an electric feed control system for wood-grinders, a main driving motor adapted to be connected with a supply and to drive a plurality of grindstones, motors for feeding the Wood forward in the grinder magazines, regulators for said motors, auxiliary motors for operating said regulators, a tap in a shunt in the connecting lead to the said main motor, relays in said shunt, coils in said relays, a regulating member for adapting said coils to relatively predetermined load conditions, and further coils in said relays adapted to be controlled by the rotor current of the remaining feed motors.

In testimony'whereof I aifix m signature.

WILHEL STIEL. 

